A useful printing density range for a visually acceptable gray scale requires approximately ten steps of density change between "white" and "dark". In an ink jet printer, where droplets of ink are expelled from a transducer chamber through discharge orifice by some form of mechanical force such as a vapor bubble produced by a discharge resistor, various methods have been tried to produce such a desired gray scale range.
A first method which depends on controlling the volume of the droplets of expelled ink over a 10 to 1 range has unfortunately proven extremely difficult.
A second method requires adding or deleting drops of ink from individual picture elements (pixels) that create the picture cells. This will produce the desired gray scale effect, but at a substantial reduction in resolution since with any given drop size and discharge orifice spacing, the resolution is reduced by the square root of the number of gray scale steps within each picture cell.